The effects of kanamycin ototoxicity in humans have been well documented. Animal studies indicate that initial damage to the cochlea begins in the basal turns, spreads to the apex, and eventually envelops inner as well as outer hair cells. However, no animal data exists concerning the effect of kanamycin upon intensity and frequency discrimination, or upon energy integration. Previous studies with the cat have produced cochlear damage by acoustic trauma, but were unable to show changes in these functions. It is the intention of the proposed research to investigate changes in these functions as a result of minimal kanamycin damage to the cochlea in rats. The basic methodology will involve the psychophysical techniques of constant stimuli and signal detection. Pre and post drug behavioral audiometry will be correlated with post-mortem histological findings. We hope that the observed changes will elucidate the mechanisms of intensity and frequency discrimination, and energy integration, perhaps as a function of differential damage to outer and inner hair cells. We also hope to continue the development of the psychophysics of animals, permitting finer measures of discrimination in shorter time periods.